I started growing 6 Orange Tendersweet watermelons from seed in late-ish May. They were slow to get going at first, probably due to cooler temps, But then about 4 weeks ago they really took off, and so did my cukes.

I checked on the plants on Friday, then again yesterday, and yesterday I noticed some leaves yellowing on certain vines. These plants are close to each other and the vines are touching because I had limited sunny space, and because they grow lots of lateral vines. But as I looked through them, I could see that the yellowing was happening on leaves from 2-3 particular plants, but not yet on others. Its possible they had started yellowing last friday but I just didnt notice it yet.

The yellowing starts out near the leaf edges, then towards the veins in the central areas of the leaf, but the vein area is still darker green. The leaves werent yet completely yellow. On the leaves that seem to have been more affected(or affected for a longer period ??), they show little round, light to medium brown spots on the tops and bottoms of the leaves. These little brown spots are approx. 2-4mm in diameter.

In some cases, the brown spots have a light straw colored spot within the little brown spots, sort of like the brown spot is turning a light tan-gray color. They look almost off white. On others, the brown spots are much darker, like a burnt blackish brown color, and these spots are a little larger.

Now, the other 3-4 plants dont show these symptoms yet, and are still green. I noticed on one affected plant, that the yellowing leaves ended halfway up the lateral vine, and the newer leaves on the far end of the vine werent yet yellowing. That particular vine had grown up into an azalea, so that the end part(which was still green) was partly shaded from sun, whether that has any bearing on this I dont know, but I thought I'd mention it.

I looked up these symptoms on the web, and found numerous possible issues, mostly disease related, and I dont see any insects on them, so it may be a fungus or disease. So, I had some Immunox with me, and its labeled for watermelons, so I applied an application to the leaves using a hose end sprayer at 1.5oz per gallon(the instructions on the bottle(1oz) contradicted the online instructions which called for 1.5oz).

I dont know if that will help or not, but its the best I could do on short notice. They have not been overwatered by me, but we have gotten a few hard thunderstorms occasionally. I know they havent been underwatered at least.....

Any ideas? Will the Immunox help, or at least will it prevent disease from spreading to unaffected plants? If not disease related, can they be saved?

Thanks